Driving After Dark

In the trucking business, neither management nor labor always knows ahead of time when a load will need to be moved. Pick-up and delivery times are made based on the needs of customers.

While management tries to coordinate its customers’ needs with the requirements of the law and the physiological requirements of drivers, delivery schedules do not and cannot take into account the fact that the night is made for sleeping.

Sleep scientists tell us that our biological cycles of activity are regulated by circadian rhythms. These rhythms of relative wakefulness are generated by an internal clock that is coordinated to lightdark cycles. As night falls, a hormone called melatonin is released into our brains. This hormone induces sleep. Yet, while there are other periods of low biological activity, particularly mid-afternoon, our minds and bodies are naturally geared to sleep when the sun goes down.

Dr. Richard Grace, of Carnegie Mellon’s National Robotics Laboratory, says, “This need for sleep is particularly strong between 2 and 6 o’clock in the morning. Drivers who constantly drive at night can become sleep deprived even though they may not exhibit sleep-deprived-performance problems. But these same drivers also lose the ability to perform at a high level.” The freight, nevertheless, must move.It is, therefore, fortunate that truck driving requires a constant low level of mental activity rather than an extremely high degree. The decisions a driver makes are often small, though significant. Adjustments to steering, the tiny muscular movements which keep a truck centered in its lane, are examples. Every steering adjustment is a decision. Glancing in the mirrors is a decision. Even pulling the eyes back to the windshield from the mirrors is a decision. When the melatonin is flowing and visibility is lessened by darkness, two strong negatives affect a driver. While he may be able to safely continue making low-level decisions, his reflexes may be slowed at exactly the moment when it is necessary to make instant and accurate decisions of the most significant kind.

In a report entitled, “Fatalities and Injuries in Truck Crashes by Time of Day,” prepared by Daniel Blower and Kenneth Campbell at the Center for National Truck Statistics for the Office of Motor Carriers, the authors note that, “Using exposure data classifying night as between 9 p.m. and 6 a.m. truck travel during that period is associated with a relative risk about twice that of the rest of the day.” Crashes at night are also more severe. According to the report, there are about three times as many fatalities per thousand crashes between midnight and 6 a.m.

The report says that fatigue is indeed a significant factor in single vehicle fatal crashes involving trucks. In other words, drivers fall asleep and run off the road more at night than during the day. But the risks do not come only from the drivers of trucks. “Almost 40 percent of the nontruck drivers in multiple vehicle crashes with trucks between midnight and 3 a.m. had used alcohol, compared with 2.7 percent of the truck drivers.

Fatigue also was coded more often for nontruck drivers than for truck drivers in multiple vehicle crashes.” The professional driver who is required to maintain delivery schedules around the clock is fighting not only his fatigue and his reduced sight distances, but also he is fighting factors, like alcohol consumption in the nonprofessional highway population. Perhaps a night driver’s only saving grace is the relative lack of nightly traffic.

A professional driver survives because he has developed and constantly refines his situational awareness. As night falls, this awareness must include the new variables that decreased visibility and increased fatigue help to create. Drivers are notoriously bad at evaluating their fitness for duty, which means that many drivers are fatigued enough to impair their driving skills long before they are willing to admit it. It is also quite common to find the pro outdriving his headlights without realizing it.

Today’s headlights on low beam provide a lighted range of between 300 and 350 feet, high beams about 500 feet. On long stretches of rural interstate, it is easy to ratchet up speed and forget that stopping distances can begin to outpace visibility. Headlights illuminate much less of the world one sees through the windshield than does the sun. Peripheral vision is at an absolute minimum at night, allowing the stray deer to become a potentially lethal, if nearly invisible, hazard. In urban areas, the constant glare of headlights from oncoming traffic adds frustration and eyestrain to an already toxic mix of negative inputs.

Headlights, mirrors and windows obscured by dirt, rain, snow and ice further reduce visibility. It has, until recently, been difficult to keep headlights and windshields clean on a constant basis. Cleaning them at fuel stops is a necessity, but the effect of this effort is quickly lost in bad weather. Two new products from Trim Systems, formerly Commercial Vehicle Systems, help keep visibility at optimal levels on a constant basis.

Lightwatch is a headlight washing system available on some new model tractors as well as from dealers as an aftermarket product. Lightwatch literature says that its washer will remove even ice from headlights, a godsend to drivers whose only method of keeping lights clean has been to stop and clean them by hand. Clearview is a heated windshield cleaning and deicing system engineered to work with existing washer systems. It heats washing fluid to a preset temperature and applies it to the windshield in 10-to-40 second intervals unless it is turned off by the driver. For more information, Trim Systems at (800) 441-2048.

Even more common than weather as a culprit in reducing visibility is glare. And while fleet drivers may not be in the market for aftermarket add-ons to their trucks, they can reduce glare by purchasing a pair of yellow tinted sunglasses. This product is used by drivers on the ice roads of Canada’s Far North to cut the glare of sun on snow, and it is just as useful for highway night driving in the comparatively balmy conditions in the Lower 48. All of these products can be useful.

However, the resourceful driver realizes that his safety depends on his ability to remain alert and to anticipate problems hidden by darkness. Limited sight distance on hills becomes even more critical since headlights do not illuminate the roadway as the truck is cresting a rise. Anything in the road, on the other side of a hill or around a curve is even more obscured from view. Adjusting one’s speed and vision to the very edge of headlight range are the only ways to ensure safe transit through limited sight distance situations.

The intimate connection between sight and wakefulness is perhaps the most singular aspect of night driving under a driver’s control. Being aware of one’s personal biological low spots can sometimes help a driver schedule his more difficult hours. Contrary to accepted wisdom, some drivers, like Curt Steffler, an owner-operator for Jones Motor, find night driving the most productive time to work. Steffler says, “I always seem to cover more ground at night. On a long ride I drive until 3 or 4, and then sleep until I wake up.” Circadian rhythms are personal, as Steffler’s experience suggests. Thus, it may be true that his biological clock allows him to drive nearly all night.

On the other hand, he may have simply gotten used to the necessity of his work, as Grace has suggested is often the case for drivers who work all night. No matter how used to driving all night one gets, the possibility that fatigue or poor visibility plays a part in creating dangerous driving scenarios remains. Knowing when one needs sleep and turning that knowledge into behavior is a survival skill.

Is it possible to fight fatigue? Is it possible to will oneself to stay awake? The answer is no, according to sleep scientists. At some point the body’s need for rest will overcome the attempts of the conscious mind to remain wakeful. Stuck between a delivery time and a biological need for rest, the driver’s best weapon against fatigue is self scheduling. From knowledge of his personal internal clock, a driver can regulate his day more efficiently.

Grace found in studies of LTL drivers that taking a nap at the first onset of fatigue added more waking time at the end of drivers’ shifts.

What does a driver do to stay awake between spots where he can pull off to sleep? Certainly, there are times when sleep catches up to a night driver, taking him by surprise. One technique that may work for some drivers in emergencies comes from yoga. Breathing is a very important part of many yogic practices. It is said to restore energy by sending large amounts of oxygen to the blood. Yogis have practiced various breathing techniques for thousands of years to refine these techniques.

One such technique, long deep breathing, is simply pulling as much air into the lungs as possible through the nose until the lungs are full. The breath is suspended for a few seconds and then expelled completely. Repeating this a few times sends oxygen to a fatigued brain and will provide temporary relief from overwhelming fatigue. It is a technique that will get a tired driver to the next rest area. It is not meant as a substitute for bunk time.

While drivers struggle to stay awake and see, scientists are hard at work devising new technology to make night driving safer. The Perclos camera, a windshield mounted camera that measures percent of eyelid closure, gives a driver objective feedback about his level of wakefulness.

Smart cruise control systems, lane tracking devices and collision avoidance systems will help lower accident statistics when they become available. The Bendix Xvision infrared night vision system uses heat sensors to extend awareness of low contrast objects to 1,500 feet, according to Andrea Raaber, director of new ventures for Bendix Commercial Vehicle.

This system will extend a driver’s vision of low contrast objects five times, Rabner says. The Bendix system is mounted above the windshield and is used as an aid to driving rather than as a drive-by system, according to Raaber. The system will image any object with a temperature more than 0.2 percent different than the outdoor temperature. Bendix plans to introduce its Xvision system late in the second quarter this year.

Despite the promise of technologically improved night driving capability, drivers will always need to rely on themselves to stay between the ditches. New technology will prove its usefulness over time, but it must first be accepted by drivers. In the meantime, driving at night will continue to be twice as dangerous as driving in daylight.

If you drive when the sun doesn’t shine, make yourself a safer operator by doing what you can to improve your vision and your wakefulness with a little self-knowledge and a whole lot of common sense. A life will always be worth more than a load of freight.